题目内容：

The first thing_______my brother is going to do this afternoonis to write a letter.
A which B that C why D who

优质解答

B that

追答：

1.这是一个定语从句，先行词不是人，所以排除C why D who. 2.当先行词被序数词修饰时，关系词只能用that，不能用which（这个要记） first 是序数词